I had never taken a look at the difference in OGRE miniature castings… Compare below two Mk. Vs – the left one is a “modern” Mk. V while the one on the right is from Martian Metals in the ’80s:

(The right one is actually labeled “Mk. Vb” by Martian Metals. Misprint, or alternate chassis?)

Check out the stylings on the front of the OGREs; the Martian Metals version has a pointed ‘hull’ that looks particularly cool. The newer casting has a lot more details, and the external missiles are housed in armour.